NTN Steel Bearings are the ultimate. Here is why...
NTN Seal Info; http://www.ntnglobal.com/en/products/...
Check out Hambini's excellent analysis; http://www.hambini.com/bearing-perfor...
Not spam, just an offer; if you want some NTN bearings, I can send you some from here in Japan. Message me or comment, and we can sort it out. (^-^)v